Hydrogen production from water electrolysis is a key enabling energy storage technology for large scale deployment of intermittent renewable energy sources. Proton Ceramic Electrolysers (PCEs) can produce dry pressurized hydrogen directly from steam, avoiding major parts of cost-driving downstream separation and compression. The development of PCEs has however suffered from limited electrical efficiency due to electronic leakage and poor electrode kinetics. Here, we present the first fully-operational BaZrO3-based tubular PCE, with 10 cm 2 active area and a hydrogen production rate above 15 NmL•min-1. The novel steam anode Ba1-xGd0.8La0.2+xCo2O6-δ (BGLC) exhibits mixed p-type electronic and protonic conduction and low activation energy for water splitting, enabling total polarization resistances below 1 Ω•cm 2 at 600°C and faradaic efficiencies close to 100% at high steam pressures. These tubular PCEs are mechanically robust, tolerate high pressures, allow improved process integration, and offer scale-up modularity. High temperature electrolysers (HTEs) that utilize readily available steam and/or heat (renewable or industrial) as a supplementary energy source provide superior electrical efficiency compared to conventional water electrolysis. 1-4 HTEs developed to date comprise solid oxide electrolysers (SOEs) which utilize oxide ion conducting electrolytes and therefore produce hydrogen on the steam side cathode. The undiluted high pressure oxygen produced on the anode in SOEs presents a safety hazard. Their high operating temperature (typically 800°C)
Conventional production of hydrogen requires large industrial plants to minimise energy losses and capital costs associated with steam reforming, water-gas shift, product separation, and compression. Here we present a protonic membrane reformer (PMR) which produces high purity hydrogen from steam methane reforming in a single-stage process with near-zero energy loss. We use a BaZrO 3 -based proton-conducting electrolyte deposited as a dense film on a porous Ni composite electrode with dual function as a reforming catalyst. At 800 °C, we achieve full methane conversion by removing 99 % of the formed hydrogen, which is simultaneously compressed electrochemically up to 50 bar. A thermally-balanced operation regime is achieved by coupling several thermo-chemical processes. Modelling of a small scale (10 kg H 2 day -1 ) hydrogen plant reveals an overall energy efficiency of >87 %. The results suggest that future declining electricity prices can make PMRs a competitive alternative for industrial-scale hydrogen plants integrating CO 2 capture.Membranes that simultaneously enable chemical reaction and product separation hold promise for process intensification 1-3 . Currently, the most energy efficient production pathway for hydrogen from methane combines steam reforming (CH 4 + H 2 O = 3H 2 + CO, ΔH 1073K = 226 kJ mol -1 ) and water-gas shift (CO + H 2 O = H 2 + CO 2 , ΔH 1073K = -34 kJ mol -1 ) in a multistep process 4 , where heat management is crucial. The produced hydrogen is conventionally separated downstream using e.g. pressure swing absorption (PSA) 5 . Alternatively, hydrogen separation can be included in the steam reforming process using hydrogen selective membranes 6,7 with the benefit of simultaneously separating hydrogen while shifting the thermodynamic equilibrium resulting in process intensification. Most practiced membranes are metallic, predominantly based on Pd or Pd-Ag alloys 8 . The separation is driven by the hydrogen partial pressure difference across the membrane, from which it follows that the pressure of the produced hydrogen is low, and further
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